Err. Mines prettier?
*cough*
Only real difference is ${2:-yes} versus ${2-yes}; the latter should
be used so that `usex flag '' '--disable-some-feature'` is usable.

> > While a bit longer, we likely can gut most of the use_* logic to
> > use that, and it makes it easier to deal w/ the situations where a
> > configure's options always assume --enable-blah thus don't export the
> > option, but *do* export a --disable-blah.
>
> yeah, i thought about replacing use_{with,enable} with usex, but we'd have to
> extend usex() a little bit more

Only extension I can think of is adding a prefix/postfix... which
frankly seems a bit too much. Anything else you were looking for?
To be clear, I'm more interested in this from the standpoint of making
econf invocations simpler- simplifying use_enable/use_with in the PM
isn't a huge concern to me since they're already pretty bloody
straightforward at this point.
~brian